Our 60-something-year-old tour guide probably wishes he had opted for an "electric-assist" model when we collected our rental bikes this morning.
About two-thirds of the way through our 24-kilometre ride along the Shimanami Kaido cycling route, he is somewhere near the bottom of the coiling approach track to Ikuchi Bridge.
While his three Australian guests await him near the top, we Instagram pictures of the spectacular cable-stayed bridge, which links two of the islands in the Seto Inland Sea that we are journeying through.
When, however, he still hasn't appeared after half-an-hour, I double back. I find him, red-faced with exertion and embarrassment, toiling on the track's first incline.
Peeling the heavy rucksack off his back, we agree to walk our bikes uphill.
Once he gets his breath back, the slower pace encourages the long-time denizen of nearby Hiroshima to talk.
"It was very sad, the atomic bomb is kind of the endless story," he responds to my question about the events of August 6, 1945.
This was when the US dropped the first deployed atom bomb on Hiroshima, killing 80,000 people immediately and destroying 90 per cent of the city. Tens of thousands died later from the effects of radiation.
"My mother's father was working for the civil service and was right close to the bomb," he says. "He was rescued but so badly burnt he died a week later, at just 42.
"His father died 10 days later from shock."
Climbing this curling slope overlooking the tranquil Seto Inland sea, two hours from the epicentre of that explosion 71 years ago, it's hard to imagine the devastation.
"On the other hand, my other grandfather was lucky," he continues. "He missed his 7am train into work that day.
"In the end, he came into the city to help people and, although exposed to radiation, survived until the age of 82."
"The recovery in Hiroshima," he ends his testimony by saying, "is amazing".
Having spent last night in the buzzing modern city, and lapped up a theatrical okonomiyaki (savoury pancake) feast for dinner, it is easy to concur.
Hiroshima now hosts one million tourists a year; many, it seems, visiting to commemorate the event that changed the world forever. In May 2016, erstwhile President Obama became the first sitting US leader to pay his respects, laying a wreath at Hiroshima's memorial peace park.
While it is impossible to ignore Hiroshima's horrible history, this 74-kilometre cycling route provides added incentive for a visit to the region.
Skirting the coast of several craggy islands in the Seto Inland sea, the Shimanami Kaido route was recently named among Lonely Planet's top 50 "epic bike rides of the world".
We begin our cycle by picking up rental bikes and although not compulsory in Japan, helmets, at the train station in Onomichi, Hiroshima prefecture's second city, 80-minutes away by train.
On our short ferry ride to our starting point on Mukaishima Island, we trace our route on a bike map, hardly noticing the occasional "steep hills, you can do it" annotation.
From the ferry terminal we follow a blue line on the road out of town and along the coast.
The Seto Inland Sea was one of Japan's first national parks, declared in 1934, and encompasses 3000 islands and islets, three of which we cycle.
Each island, from Mukaishima to Innoshima, where we pause for lunch, to Ikuchima, where we end, has its own flavour but all are predominantly green and covered in citrus trees. In an area known as the "orchard of Japan", some of the mandarins we see dangle as plump as grapefruits from the tree.
Much of the route is also the antidote to Japan's freneticism, with fishing villages abandoned for the city by the young and an emerald sea lapping the islands' shores.
Yet contemporary Japan is all part of the scenery. Tugboats and tankers chug offshore and we cross some impressive bridges, including the 1300-metre Innoshima suspension bridge, which we cycle beneath on a metal carriageway, as cars rattle speedily above our heads.
The whole 74-kilometre route can be ridden in a day by regular cyclists or in two by those not used to hours in the saddle.
But for me, and our guide, covering a third of the Shimanami Kaido route, is enough, especially in the cold afternoon rain.
With the end, at a rental station at Setoda port, almost in sight, our guide finds his cycling legs, leading us at pace along the final straight.
His earlier difficulties have undoubtedly enriched the adventure, adding personal history to my experience of this captivating region.
Japan Airlines fly to Hiroshima from Tokyo's Haneda airport; journey time 90 minutes. au.jal.com
The route's starting point, Onomichi station, is about 80 minutes from Hiroshima.
Bikes can be rented at 13 terminals along the route, from ¥1,000 ($11.40) per day plus ¥1,000 deposit. See go-shimanami.jp/global/english/bicycle/
Daniel Scott travelled courtesy of Japan's National Tourist Office.